


In This World, It's Treat or be Tricked

by Ononymous



Category: Undertale (Video Game)
Genre: Gen, Post-Undertale Pacifist Route, Trick or Treating
Language: English
Status: Completed
Published: 2017-10-31
Updated: 2017-10-31
Packaged: 2019-01-17 18:13:54
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,027
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12371265
Author URL: https://archiveofourown.org/users/Ononymous/pseuds/Ononymous
Summary: Sans has made the perfect plan to be in the perfect place this Halloween. At home, watching TV.





	In This World, It's Treat or be Tricked

His preparations were nearly complete. He'd been planning for weeks. After being caught off guard the previous year, he would not suffer such an indignity again. Dusting off books he hadn't touched in years, except to get them out of the Underground. Sending his brother to pick up supplies. Hell, he'd even grabbed a couple of things himself. If everything played out like he hoped, this evening would go smoothly.

 _PING. Thud!_ "done."

He eyed it carefully. Hmm, maybe if he moved it a little... There it was, the perfect angle.

"SANS! I'M LEAVING SHORTLY..."

A large grey box entered the room. Its yellow and red screen turned to look at the recliner chair. White gloved hands fumbled for a latch, and the screen lifted up to reveal a skull beneath it. His sockets moved to the two small tables flanking it, the one nearest the door with several bowls of candy, the other with assorted snacks and a large bottle.

"WHY HAVE YOU MOVED THAT CHAIR?"

"so i don't have to get up to open the door."

"I CAN'T BELIEVE IT. EVEN WHEN YOU ENGAGE WITH THE FESTIVITIES YOU DO IT IN THE LAZIEST WAY POSSIBLE."

"i know. i'm proud of me too."

"ARE YOU SURE YOU DON'T WANT TO GO TO METTATON'S PARTY? MOST OF OUR FRIENDS SHOULD BE THERE."

"thanks, pap, but i'm all set up for tonight. i don't wanna ruin my costume."

"WHAT COSTUME? YOU'RE WEARING YOUR NORMAL CLOTHES."

"you missed my monocle. see?"

"SO WHAT DOES THAT MAKE YOU?"

"myself if i had bad eyesight in one socket."

Papyrus stroked his chin. "HMM, A SUBTLE DISPLAY. I LAUD YOUR CUNNING, BROTHER! MEANWHILE EVERYBODY SHALL BE IMPRESSED AS A SECOND METTATON ARRIVES! I WONDER HOW LONG I CAN FOOL THEM?"

"uh, don't he normally have wheels in that form?"

"YES, BUT I COULDN'T MASTER THE UNICYCLE IN TIME. SO INSTEAD I PAINTED MY BOOTS PINK, SEE?"

Sans adjusted his monocle as he examined the slightly wet boots. "pretty cool, bro. you'd better _leg_ it if you wanna get there in time."

"INDEED!" He slammed his screen back down again. "I SHALL HAVE MY PHONE IF YOU NEED ME! NYEH HEH!"

The Two-Foot-Taller-Than-Usual Mettaton strode out the door and closed it behind him. Sans put the final part of his plan into operation. He strode over to his chair, planted himself deep enough to touch bedrock, grabbed the remote and turned on the TV. _Perfect._

As fun as watching TV underground had been, Sans was grateful for the variety humans put into wasting their time. There was only so much you could veg out to Mettaton. However variety wasn't as plentiful tonight as one might expect. It didn't take long for a pattern to emerge.

"superhero encounters a monster... cops encounter a monster... rockstar encounters a monster... monster encounters a monster, heh, that's new... cool, the weather channel."

As seasonal as the Underground could be, it was a drop in the bucket compared to what the surface had to offer. And in between repeatedly telling him how tonight would be dry but cold and there would be drizzle tomorrow morning, the channel captured his attention with footage of what weather could be really like. Trees uprooted by the wind. Before and after shots of rivers drying up in scorching heat. Monsoon rains you didn't walk through as much as swim through. Doors completely blocked by snow and ice. Dramatic thunderstorms with lightning bolts miles long. Ships rocking in waves thrice their height. All of this punctuated by peaceful rainbows. Many monsters could produce a rainbow with a literal snap of their fingers, but there was something about natural ones that caught his attention. Just as coming to the surface meant challenges and difficulties making peace with humanity none of them could have appreciated, the likes of Snowdin were mere training wheels for what the sky could throw at them without even dealing with a single human.

Not that Sans considered the allegorical implications of weather for their diplomatic situation. He was too busy grabbing some popcorn.

It was as a documentary about a famous hurricane started up and he pondered jumping ship to another channel that the doorbell rang. With a wave of his hand, the handle shimmered blue and the door swung open.

"Trick or treat!"

He swivelled round in his chair to at least show some manners. That modification Alphys did for him was a great job. A pirate, a ballerina and a cop headed a small column of human children.

"Woah, nice costume, mister!" said the ballerina

"heh, thanks kid. i like yours _too-tu_."

As the children giggled he grabbed one of the candy bowls, scooped a large handful and threw it at them. To their amazement, the loose ball split into half a dozen fragments that landed neatly into each bag. They hadn't noticed the flash in his socket.

"That was awesome!" cried a lion at the back. "How'd you do that?!"

"practice. not everyone can do it, but the _mane_ thing is you try."

Delighted with the impromptu and literal magic trick, the kids walked back to the street babbling excitedly. The door swung shut behind them without anyone touching it. Okay, back to the important business. Was there any wrestling on? The answer turned out to be no, but he did find a show where a chartered accountant encountered a monster, and he was so impressed at the original idea he watched it for a while.

"huh, never thought itemizing a haunted house could be so engaging. gotta _account_ for that in the future."

The doorbell rang again. Like before he opened it and swivelled round.

"Yo, Sans! Trick or Treat!"

There were a few ways he knew he was dealing with monsters this time. For starters they knew who he was. Also all the costumes were of mundane jobs. Monster Kid led the way as a chef, while the smaller monster to his left was a waitress. They were accompanied by another cop, a firefighter, a doctor and a builder. The final clue was they all wore the same mask of a tanned face and narrow eye slits. MTT™ Brand Human Masks. Monster Kid and his little sister also had fake arms strapped to their shoulders to complete the effect, and he was holding both their bags on his tail.

"s'up. cool human costumes, guys," said Sans, as the six of them walked up to get their candy, "though maybe the tails kinda ruin the effect."

"They do?" asked the doctor, who tried to tuck her own furry tail under her coat.

"Wait," said the builder, "you mean humans don't have tails at all? I thought it was just some."

"when it comes to bones, nobody knows more than me, buddy."

"But I saw one!" squeaked Monster Kid's sister. "On TV, a human was playing pool, and he grew one!"

"Sis, that was Pinocchio," her brother corrected, "it's just a cartoon. I don't think it's real."

"Oh..."

It was too early in the evening for dashed dreams. "welp, maybe i got it wrong. frisk might know better, or at least _marrow_ down the possibilities. see ya, kids."

Thanking him for the treat, their debate about human anatomy continued, the cop closing the door as they left. Another episode of the show with the chartered accountant started, and Sans gave it his undivided attention. Or at least he planned to, when the doorbell rang again.

"Hey, can I sign onto your wifi a minute-"

The door closed in his face.

This was how the evening progressed for a while, his successful TV marathons punctuated by giving out candy. Most of the groups were not entirely human or entirely monster unlike the first two, but a mixture. Frisk's influence at school was hard to resist. The groups of kids were broken up by adult monsters saying hello, most seemingly heading to or coming from Mettaton's party. As the night progressed, his satisfaction at his preparations grew. He wasn't watching quite as much as he hoped, but at least he hadn't been forced to walk from the couch to the door and back repeatedly and miss whole scenes in the process. With all the energy he'd saved, he might not even need a nap before bedtime at this rate.

Late in the evening, down to his last bowl of candy and enjoying a movie about an airplane in trouble, the door knocked roughly. Once again he swivelled round.

"s'up, ki-"

He halted. This crowd was different. Four humans, taller than most of his guests, probably teenagers. None of them were in costume, but one was wearing a skeleton mask. They each had large full bags, and Sans didn't know of any candy that large.

"heya," he started again, "you kids been busy?"

"Yeah, you could say that." replied the guy in front, not looking like he cared. "Trick or treat."

As before, Sans tossed them piles of candy. The leader looked at the sprinkling now covering whatever was in his bag with an over the top look of apology.

"Ohhhh, sorry, I can't eat this."

Sans' fixed face remained fixed. "why not, buddy?"

"I'm diabetic. Sugar's bad for me."

He racked his skull trying to recall the term. Some human bodies couldn't digest human food properly, right? "don't worry pal, that's all monster candy. turns straight to energy. no sugar to worry about."

"Oh, you're a monster?" His surprise was less than sincere. "I just thought that was a costume."

"well i'm pleased with my monocle-"

"Anyway, even if I can eat it, it might encourage me to take on bad habits. Best if I just get a different treat."

"well my brother made some spaghetti earlier, if you can get _pasta_ the taste. or I've got some popato chisps. dunno what kinda treat you want otherwise."

"Well, how about some money?"

His three friends chuckled.

"didn't think that was a thematically appropriate treat, kid."

"Well you haven't been round here long. Perfectly normal to get cash treats. We made a killing on the far side of town. Is it true you use gold to pay for stuff?"

"nah, got myself a visa card. way less bulky to carry around, to its _credit_."

"So you don't have any money? That's a pity. I heard there's a rough crowd going around, and they don't take no for an answer." His friends laughed again.

"izzat so?"

"Yeah. So maybe we should make sure you don't have any-"

"no thanks."

His tone hadn't changed at all, but the guest's leg, which had just crossed the threshold of the house, froze above the welcome mat. Slowly it returned to its starting position on the porch.

"appreciate your neighbourly concern, amigos, but i've got it covered. can't offer you anymore in the treat department, I'm afraid. if there's really a rough crowd out there, you'd better go home. wouldn't want your folks to worry about you. by the way you've _goat_ to try the butterscotch pieces, a friend of mine made 'em. later."

He closed the door firmly. Turning his attention back to the movie for a moment, he sighed, then hit record. Outside, tempers were flaring.

"Goddamned smartass sack of bones," growled the leader, "looks like it's trick time! Julie, got the bag?"

"Right here." she fished it out of her bag and held it at arm's length as she fished for a lighter in her pocket.

"Roy, Juan, teepee duties."

"Sure thing, Kev." They retreated to the street and started extracting supplies from their own bags. They assembled a small stockpile of ammunition.

"And hey, that's a pretty neat lantern," said Kev, "too bad."

He raised a heavy looking boot. The pumpkin with Papyrus' earnest grin sat on the ground, about to suffer for its naivety.

But as the boot came thundering down, the pumpkin suddenly slid ten feet away. A dull ache started up in his foot as the expected cushioning did not arrive to soften the sharp thud.

"Ow! What the-"

He wheeled round to see how Julie was getting on. She had just lit the top of the bag and was positioning it on the front door. And then she was recoiling. The bag had zoomed from its position, so fast the small flame went out, and slammed into her shirt. A foul smell made itself known.

"Oh, ugh! Eww! Son of a-"

"Hey, stop it!"

They both looked at their accomplices. Juan had thrown a roll of toilet paper at the house, but even as it unspooled, it changed course and fell back to him, lightly tapping him on the head. This was the starting whistle for their stockpile to shimmer blue, come to life and start playfully hitting them, or otherwise similarly unspooling and trying to wrap them like a makeshift mummy.

"Get off! Get off!"

Now Kev and Julie's bags came to life too. More toilet paper began to assault all four of the would be assailants, but there were now other hazards to contend with. A can of paint sloshed Roy. A second paper bag hit Juan in the face, not improving the smell. Firecrackers fell to the ground and started detonating, the noise utterly panicking them. Soon Roy had broken his surprisingly tight bounds and was making a bewildered retreat, followed closely by a retching Juan and a Julie trying to dodge the paint. Kev was bound in place by his own two-ply bindings, and when he finally tore them, he lost his footing and fell over.

Flipping onto his back to get up, he suddenly felt weighed down. The first thing he saw were the slippers. He then looked up the silhouette they belonged to. One socket was entirely devoid of life. The other had a brilliant light that flickered blue and yellow.

"Y o u s h o u l d h a v e t r i e d t h e b u t t e r s c o t c h."

Another large shadow appeared, six foot off the ground. But it wasn't left in darkness for long. A glowing light in its mouth revealed it to be a skull not unlike a dragon's. And whatever was glowing, it was pointed right at him.

Forgetting he had been weighed down, and not noticing he had been released from such, Kev sprang to his feet and fled, screaming the whole way. The skull vanished.

"heh. stupid doodoo butts."

Sans made his way back inside. This would cause quite a headache for the King in the morning, especially if it devolved into he-said-they-said. But fortunately it wouldn't go that far. Alphys had suggested setting up CCTV around places monsters usually were in case such an altercation broke out. When the footage was examined in the morning, it would be pretty clear it was only when his guests had been less than gracious that Sans caused mischief. The finishing touch might have been a bit much, but as he'd argue, they threatened his brother's really cool lantern. Frisk would probably be the best one to look at the footage first, they might be able to give some advice.

Not that Sans considered the ramifications of his actions or the best course to mitigate them. He was too busy rewinding the movie.

The festivities of the evening were winding down now. Most of his callers now were just stopping in from the party. Dogamy, dressed as a barbarian, invited him too head round for a poker game while Dogaressa lingered at the party, but Sans declined. Among the well wishers there were only a couple more trick or treat groups, but they still managed to take a large supply of his candy.

In the meantime, he'd hit the TV jackpot. A human was talking passionately about quantum physics. Sans loved comedy shows like this. He knew the guy believed every word he said, but it was funny how utterly wrong much of it was. But then magic had allowed monsters to cheat a little when figuring this stuff out. One of his manuals from the old days could blow up the whole field of study. But he didn't want to part with it, for sentimental reasons.

The show wrapped up as the doorbell rang. Glancing at the bowl, there was enough for one more group. He'd call it a night. The door swung open, and a short astronaut stood alone in the doorframe, the impressive helmet's visor down.

"Haodeh," the astronaut muffled, "trurk ur treht."

"woah buddy, sure aimed for the moon with that. it's your lucky day, you get the last of my candy."

The prize soared through the air, and like nearly every other piece landed in the open bag.

"Thunk ew vurruh much, Sns."

"huh?"

"Thunk ew vurruh much, Sns."

"speak up, pal."

"Aw saod, thunk ew-"

 _PING._ The visor slid open. The occupant's furry nostrils wrinkled at the sudden rush of fresh air.

"Oh! Thanks, Sans. It was stuck. I thought I'd have to get Dad to open it when he got home."

"oh. hey, cap. flyin' solo tonight?"

"Well not at first," said Asriel, "but Frisk and I made the mistake of visiting Mettaton's house, and he ushered them in before they could object. I only got away because he didn't recognise me."

"ooh, tough luck for the kid. celebrity parties not your scene?"

"Nah, not really. I mean he'd have made a fuss because the whole Royal Family was there, and I'd have people coming up to me all night asking me how I'm doing after I managed to... well, spread my roots a little."

"heh. your mom would like that one."

"Ha ha, yeah she would. Anyway I don't mind my friends asking, but it gets tiring telling everyone I'm fine, and sometimes I end up not fine because I'm thinking about it all night, so I figured I'd knock up a few more houses before the party winds down."

"kid, if what pap tells me is true, mettaton won't release your family until the party ends, and i don't think you know how long his parties can last."

"Oh. Well I can't go to Mom's house or Dad's house, they're not there."

"no problem. come on in. our couch hasn't been sat on in hours. i'll let your folks know where you are"

"Oh, r-really? Okay..."

He looked a little nervous at the invitation, but shuffled in eventually and sat down. The first time Sans had seen him with clothes on he bordered on fleeing in terror. He couldn't blame him, even if he hadn't known why at first. But the clothes had brought on an major attitude change, so Sans was content to leave it at that. Grudges were too much effort, especially when you don't remember most of it. No use crying over spilt milk that never spilled. He fidgeted a little while Sans fulfilled his promise to text Toriel.

"want some chisps? jerky?"

"Thanks. What are you watching?"

"eh, this and that. oh cool, it's monster wrestling."

On the screen, Aaron was busy smack-talking Greater Dog, who merely barked a retort, before getting down to business. It didn't take long for both of them to choose opposing combatants and cheer them on.

"Come on, GD, watch out for his fins!"

"sorry prince, he's gonna get booped."

"Huh?"

"he'll get booped. he gets too excited and doesn't keep his guard up, an' aaron knows it."

Sure enough, Aaron had just managed to boop Greater Dog's nose, which got him rolling on the canvas quite content. Aaron capitalised by wrapping himself around his body, and Temmie the referee proceeded to tap him out.

"Aw, man!"

"sorry bucko, but i told ya so. didn't ya know that?"

"Not really, I don't get a chance to watch much. Uh, Mom doesn't let us watch wrestling."

"really?"

"You know her, she's not big on violence. Even pretend violence." Asriel reached inside his helmet to scratch. "Please don't tell her."

"don't worry. your mom's a good friend and only wants what's best for you, but she can do with relaxing a little sometimes."

"Yeah, well, you can't blame her."

"s'pose not. hey, what's on your noggin you keep scratching?"

"Sorry, it's my horns coming in. It's weird to think this will be the third time I'll have had them, ha ha."

The laughter didn't last long, but it didn't need to. Sans approved of dealing with it through comedy. With the match over he flicked the channel again, settling on a show where an auctioneer encountered a monster.

"so cap, what did frisk go out as?"

"Would you believe themselves? They got one of Mettaton's masks and wanted to see if anyone would realise. Snowdrake's dad said their jumper was the wrong colour."

"heh heh, that's a good one. well how about you? enjoying halloween?

"Oh, yeah! I mean, you know I wasn't really in the mood for it last year, but tonight was great! Seeing all the costumes and getting Spider Donuts and Temmie flakes and all sorts of candy. Oh, Mom made these!" He popped a butterscotch piece into his mouth. "Thought I'd have to wait all night for this. There's one part I don't get, though."

"really?"

"Well the humans like to try and scare each other. And mostly that's about wearing monster masks and jumping out of bushes."

"yeah, somebody looking like papyrus ain't gonna be really scary to us."

"It's not even that. I mean, when I was younger they probably would have scared me. But, well, what scares me has changed. A lot."

Sans took a drink from his bottle. It seemed to invite him to continue.

"It's not so bad now, but when I, you know, turned over a new leaf-"

"heh heh."

"-I was convinced it was temporary. That at any time, without warning, I'd lose everything. I'd go to bed half convinced I'd wake up and be right back where I was a year ago. Maybe even back underground. It's been hard convincing myself this is going to last."

He was twiddling his thumbs. He hadn't noticed that Sans still held the bottle up, despite it being empty.

"It's kind of a dumb thing to be scared of, but there it is. You know what I mean?"

"...yeah, i understand."

Asriel twigged. "Oh, golly, I'm such an idiot! Of course you know. You don't remember, but you told me once-"

"yup, i'm sure i did. least you can understand how it feels now."

Silently he passed Asriel a soda, who took a sip.

"Sorry. For bringing it up, I mean."

"don't sweat it. just a surprise you of all people can appreciate it."

He chuckled to cover his embarrassment. "Heh heh, yeah. I try not to think about it too much in any case. Frisk and Dad have been full of advice. In the end, nothing lasts forever, I might as well enjoy it while it's here."

"that's using your head, cap. 'course, you're missing three things."

"Really? What?"

"good food, good friends, bad laughs."

"Are bad laughs when you break your humerus?"

Sans' sockets twinkled with pride. "you're truly your mother's son."

"Hee hee! I guess between that and the jerky and you, I've got those three things already!"

"...yup."

It had been an unexpected development. The one most likely for filling him with disbelief and despair, and encouraging him to retreat into his jokes and naps and left him with a long lasting fear of impermanence. And it turned out he had the same fear drilled into him, albeit from a different source. That unlikely common bond could be the foundation for a friendship where once, many times, there had been naught but hostility and contempt. Or it could be a fantastic excuse to not get mad. It was out of their control now anyway. They might as well avail of this thing they had in common for as long as they could.

Not that Sans considered the opportunities for friendship or mutual support for difficult times. He was too busy telling Asriel about the teenagers.

**Author's Note:**

> Pastebin Version: https://pastebin.com/Nukch88g
> 
> Proofread by [Doogly_Writes](https://archiveofourown.org/users/Doogly_Writes/pseuds/Doogly_Writes/works).
> 
> Let me know what you think, and thanks for reading!


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